1. Field of the Invention
This invention relates to a medicament inhaler, and more particularly to a dry powder medicament inhaler activated by the breathing action of the user operable with pressurized air to emit a metered plume of dry powder particles.
2. Brief Description of the Prior Art
Dry powder inhalers are devices where a predetermined dose of medicament, either alone or in a blend with some carrier like lactose, is released as fine mist of dry powder for inhalation. These systems differ significantly from multi-dose inhalers and nebulizers in that they do not contain any liquid media (e.g. propellant or water). The drug is formulated in a manner so that it readily disperses into particles of respirable size range (i.e. xe2x89xa610 xcexcm).
Single unit dose dry powder inhaler devices are known, including some which contain multiple chambers and a selector element for releasing a dose from one chamber at a time. Relevant aspects in the designs of these devices include: establishing the correct dosage size in the device; preserving such dose from humidity and other deleterious environment elements; and delivery of the dose in a preferred particulate size within the discharge air flow.
Stated otherwise, the concerns are charging (filling) the device and storage, release, and delivery of the dose. The stored powder is, by necessity, compacted into a very small volume in an essentially solid state capsule. One of the prominent challenges encountered in design of these systems has been the breakup, or de-agglomeration, of the aggregate powder dose into a plume of fine particles which are well disbursed in the air flow. Several such devices have been developed which use a variety of methods to accomplish this end.
For example, U.S. Pat. No. 5,694,920 describes an inhalation device. Powdered medicament is stored in a blister well that is carried in a roll housed in a cartridge. Once the blister well is opened, a vibrator de-aggregates the powder in the well and keeps the powder in a fluidized state. An electrostatic plate attracts smaller particles of the powder towards the plate, where they are introduced into an air stream and carried toward a mouthpiece.
Another example is U.S. Pat. No. 6,026,809 which describes an inhalation device that utilizes vibration to facilitate suspension of a powder in a gas. A piezoelectric vibrator is used to vibrate the powder, thereby de-aggregating the powder for optimal suspension in an air stream. A controller is provided for controlling the supply of actuating electricity to the vibrator.
U.S. Pat. No. 5,033,463 describes a multi-dose inhaler for medicaments in powder form. The powder is stored in a container in the inhaler. A certain quantity of powder is withdrawn from the container and conveyed to a dispensing position by a cup. A plunger moves the powder to a mixing unit. Inhalation causes an impeller in the mixing unit to rotate, thereby mixing air and powder before it enters a user""s mouth or nose. Vibrations may be used to facilitate dropping the powder from the container to the cup.
U.S. Pat. No. 6,006,747 describes a dry powder inhaler. The inhaler includes a housing, a cartridge containing medicine supported on the housing, a lid pivotally mounted on the housing, and a mixing chamber. An impeller within the mixing chamber mixes air and the drug before they are inhaled into a patient""s lungs.
U.S. Pat. No. 5,918,594 describes an inhaling device capable of breaking down aggregates of powdered medicament to provide particles within the respiratory range. A magazine contains a dose. A de-agglomerating device is disposed in the air flow of the dose. The de-agglomerating device is made of opposing surfaces oriented obliquely to a longitudinal direction of the air flow path. When a patient inhales on a mouthpiece, the dose is drawn through the de-agglomerating device.
U.S. Pat. No. 6,003,512 describes an apparatus for aerosolizing and dispensing powders. A dose is placed into a chamber for mixing with pressurized air to break up large particles. The dose may be supplied at each administration, or the apparatus may contain a dose reservoir from which individual doses are supplied to the chamber. The dose mixture is moved through an ejecting conduit and into an exit nozzle. The exit nozzle has a sudden increase in diameter to break the pressurized agglomerates into a fine aerosol.
U.S. Pat. No. 6,029,662 describes a compressed air powder inhaler. Powder is stored in a magazine. Powder from the magazine is mixed with compressed air from an air chamber. The powder is fragmented by the flow of air and then by passing through a grille. The release of the compressed air is triggered by a patient sucking on a mouthpiece.
U.S. Pat. No. 6,223,746 describes a metered dose inhaler and pump for delivery of an active compound without the need for a pressurized active compound container.
It is seen from the foregoing that there are many existing devices which can be actuated by the inhalation of the user; which de-agglomerate stored dry powder medicament; which provide medicament to the user in a metered dosage and which are portable. However, there is always a desire to improve upon or make available alternative operating devices. Such a device should be able to accomplish these ends in an effective yet simple and possibly less costly manner than that of other designs which may be available.
It is therefore a principal object of the present invention to provide an inhaler which reliably and consistently delivers a desired dose of dry powder medicament to a user in a reasonably short period of time.
It is a further object of the present invention to provide an inhaler which administers metered doses of dry powder medicament to the user.
It is a still further object of the present invention to provide an inhaler for dispensing dry powder medicament where the device is activated by the inhalation of the user.
It is therefore a still further object of the present invention to provide an inhaler which is portable in size.
It is therefore a still further object of the present invention to provide an inhaler where each dry powdered dose is individually contained and dispersed.
A yet further object of the present invention is to provide an inhaler where after each use, a new dose is automatically indexed for the next use of the inhaler.
To attain the objects described, there is provided a device which is a breath activated dry powder inhaler. The inhaler comprises the major components of a body, mouthpiece, pressurizing and release mechanism, and a dose container, such as that, for example, set forth in co-pending U.S. patent application Ser. No. 09/756,313 filed Jan. 8, 2001 entitled xe2x80x9cDry Powder Inhalerxe2x80x9d, the disclosure of which is incorporated herein by reference.
The breath actuated dry powder inhaler operates as follows. Initially, the use manually depresses and releases the pump piston of the air pump which pressurizes air in a chamber. In this regard, the depressing action of the user compresses and forces air from a primary air chamber into a secondary air chamber. A valve between the chambers maintains the secondary chamber in a pressurized state. A transfer valve mechanism blocks a path of flow from the secondary chamber to a conduit connected to the dose to be dispensed.
When the user inhales through the mouthpiece, it creates a pressure differential across the transfer valve mechanism. As a threshold differential is reached, pressurized air from the secondary chamber causes the transfer valve mechanism to open creating a flow of pressurized air to the dose container. The pressurized air dispenses a flow of powder from the dose container whilst de-agglomerating and fluidizing the stored powder in the air flow. The powder then exits the mouthpiece to the user.